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87

This depends on how much thrust you have available. With enough thrust, you don't need to be in Earth orbit at all: you can launch straight into an escape trajectory. New Horizons did this, more or less: after launch it did about 1/4 orbit before the second stage was ignited again and insertion into its trajectory towards Jupiter began. With very little ...


70

Yet surely nobody would classify Neil Armstrong's lunar bunny-hops as suborbital spaceflights. Why not? There's no essential difference between a high-eccentricity trajectory with an apolune of 1 meter and one with an apolune of 100 kilometers. How would you define the space boundary on these planets? If the body doesn't have an atmosphere dense ...


66

The term for orbits in our solar system around the Sun is Heliocentric. Closed Heliocentric Orbit The solar observation probe Ulysses is the furthest artificial satellite around the sun. It's in a highly inclined, elliptical orbit ranging from 1.35 Astronomical Units (AU) to 5.4 AU. It was a joint project by ESA/NASA launched in 1990 and decommissioned in ...


64

Primarily, because without a lot of extra equipment, they could at best be space coffins for the astronauts. First, they share life support with the rest of the station. Air circulated through them is scrubbed of CO2 in the station's scrubbers. Heat is regulated through station's radiators. This all is powered by station's solar panels. And that's just for ...


59

The instability in orbits of our artificial satellites come from a few basic causes: Atmospheric drag and solar wind effects The Earth isn't a perfect uniform sphere but is slightly lumpy, which means its gravitational field isn't uniform Other massive objects in the solar system perturb their orbits with their gravity So let's consider them one by one. ...


59

Imagine you have a very heavy book and a bookcase, and your goal is to put the book on the top shelf of the bookcase. How much time would you spend doing that? Maybe five seconds, maybe fifteen. Would going much slower help you? No, it would not, because simply carrying the book is exhausting to you. You would never be able to hold the book up for an entire ...


57

The decision to orbit (and assemble) the International Space Station (ISS) in 51.65° prograde Low Earth Orbit (LEO) was driven by its accessibility and utility. You see, inclination changes are terribly expensive for visiting spacecraft delivering astronauts / cosmonauts, consumables, science experiments and other cargo, and ideally, you'd always launch ...


46

Zero See at: https://en.wikipedia.org/wiki/Escape_velocity for theory. Once you build enough velocity to surpass gravitational attraction, you will leave planetary orbit. A spacecraft simply circling the earth in orbit is not inherently doing anything to contribute to escaping that orbit.


43

Statement of the Problem The problem you want to solve is called the Kepler problem. In your formulation of the problem, you're starting out with the Cartesian orbital state vectors (also called Cartesian elements): that is, the initial position and velocity. As you have discovered, the only way to propagate the Cartesian elements forward in time is by ...


43

A very good question! The reason is essentially to do with tides. And a slightly over-simplified summary is: If the moon orbits more slowly than the rotation of the parent body (as our Moon does, 12 degrees per day while the Earth rotates about 360 degrees per day) then the moon will gradually orbit further and further away. If the moon orbits faster than ...


42

Essentially, this is a result of observational bias. A natural satellite will only orbit a parent for extended time periods precisely because the orbit it is in is stable †. The plain truth of the matter is that we are simply injecting satellites into unstable orbits. If you were to move natural satellites into the same orbits, they'd be unstable too. ...


42

Retrograde orbits have multiple use-cases. First of all you should note that "retrograde" doesn't mean 180° inclination - everything > 90° is considered retrograde. This places all sun-synchronous satellites which operate at about 98° inclination in retrograde orbits. The usefulness of sun-synchronous orbits should be obvious. Retrograde orbits of course ...


42

Wouldn't i inevitably spiral to sun surface even if i was faster than 0km/s ? No. On reasonable timescales, an orbit will have a fixed distance of closest approach, called "periapsis." (These timescales shorten if you're close enough to what you're orbiting that an atmosphere can drag you down). You don't really need to "drop in straight line" (which ...


40

I treated this as a problem of geometry and came up with this: The sun is the large yellow disk. The earth is the largest black disk, obscuring most of the sun The left-hand dark-grey disk is the moon as it transits across the near-side of the earth, with respect to L2. In reality in this position, the disk of the moon would appear completely black. I ...


38

Primarily, locations of spaceports would change. California, not Florida would host the NASA's main launch site. Russia would be in slightly better position, able to send rockets over the Black Sea, nicer inclinations than currently available from Baikonur - although Vostochny wouldn't happen or would be closer to Chita. ESA could forget about French Guiana, ...


36

I understand the reasons behind each of this manouveurs, however I'm wondering if this is how real rockets get into orbit. Cutting off the engine and letting the rocket loose vertical speed looks counter-intuitive to me (you basically spend a lot of fuel to accelerate and then you let the rocket slow down). In most real launches to low Earth orbit, the burn ...


35

This mission study came up with a 900 kg nuclear-electric-propulsion spacecraft launched on an Ariane V with a C3 of 100 and a Jupiter gravity assist along the way. 1.05 kW electrical power at Pluto from RTGs is required. That would be four "classic" NASA RTGs, or about nine MMRTGs. It has a 20 kg science payload. (New Horizons has ~30 kg of instruments, ...


35

To answer your title question: By using its engines. However you seems to be quite puzzled by the fact that velocity of an object can decrease and increase over the course of an orbit. If the orbit is perfectly circular, the speed will always remain the same (until thrusters are used). However, as is the case with Chandrayaan-2, most orbits are ...


34

Ultimately, "the edge of space" is an agreed upon convention. In other words it is essentially arbitrary, something which only humans even care about (well maybe space aliens too <grin>). Yes, there are various physical properties which can be used to define this boundary and the measurements themselves are not arbitrary, none-the-less, the choice of ...


33

As Undo mentioned, the type of orbit is called a retrograde. A pure retrograde orbit is quite rare, in fact, NORAD currently isn't tracking any (unclassified) objects with a 180 inclination (Pure Retrograde). However, there are a fair number of satellites with a retrograde inclination (Over 90 degrees). Of particular note is the Sun Synchronous orbits of ...


33

Physics In regards to the physics, KSP is fairly realistic, other than it not modeling n-body physics (which isn't really relevant in scope of orbiting Earth/Kerbin). In regards to the engineering, KSP makes its parts much stronger than the real life components. The tradeoff here is that when something finally breaks in KSP, it explodes and disappears. ...


32

You're confusing units. The maximum speed of the X-15 was 7274 km/h, or about 2 km/s. Orbital speed is around 8 km/s. The X-15 didn't carry enough fuel to reach orbital speed.


31

This was one of the questions just now during the Rosetta press briefing. This video was shown during the presentation: The triangular trajectory are hyperbolic orbits with respect to the comet and they'll (also, among other tasks also mentioned in the image you're attaching) serve to establish its mass. In essence ...


31

update: 6378.137 km is what I use now. By convention the altitude of a spacecraft is the distance to the center of the Earth minus roughly 6378 kilometers, or some reference radius that is representative of the equatorial radius of the Earth. Spacecraft altitude is not really used as a precise description of a satellite's position, since its only a scalar ...


31

The Answer is on a page by Sven Grahn. No ocean going tracking ships were used. Only ground stations on the territory of the USSR. In the other answers some russian sources about the use of tracking ships were found, so the information from Sven Grahn may be partialy wrong. Short waves were used for long distance (5000 km) transmission even beyond line-of-...


30

Twelve Apollo astronauts landed on and walked on the Moon Twelve more Apollo astronauts orbited the Moon without landing So that's twenty-four individuals that count towards "(except for the moon of course in the '60s/'70s)" Incidentally, as @ takintoolong just pointed out, the answer to Which astronaut travelled farthest from Earth? is the Apollo ...


29

Is the orbit shown in the graphic wrong, or is my understanding of orbital mechanics lacking, having only been influenced by KSP? It's not an either-or question. The graphic is "wrong" from the perspective of an Earth-centered inertial frame. That graphic instead uses a synodic frame, a frame that rotates with the Earth's orbit about the Sun. You can tell ...


29

I'm afraid you are incorrect. An object on the equator of Earth has a velocity of ~460 m/s. A satellite in geosynchronous orbit has a velocity of ~3000 m/s. You may be confused by the fact that both objects complete an "orbit" in 24 hours. But consider the fact that the satellite travels a significantly greater distance in that time.


28

I feel the need to correct some issues that were brought up in the other answers. Yes, gravity is an attraction-only force. But due to its relative weakness, objects in space can attain large velocities, before getting the chance to collide with any single target. In physics we would speak of excess angular momentum, which is hard to get rid of in space, ...


27

This is a great question. I wanted to provide an answer which cited some specific, real-world situations. Currently the only people in space are those aboard the International Space Station. If anyone could potentially get into a scenario as you describe in your question, it would be them. Currently, on spacewalks, a huge number of safety procedures are ...


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